LEDs are known for use in general lighting applications to provide a highly efficient and long-lasting light, sufficient to illuminate an area in home, office, or commercial settings. A single LED can produce a bright light in the range of 1-5 watts and emit 55 lumens per watt with a life expectancy of about 100,000 hours. The total luminance increases by using a light engine having banks or arrays of LEDs.
The light engine typically includes a high thermal conductivity substrate, an array of individual LED semiconductor devices mounted on the substrate, and a transparent polymeric encapsulant, e.g., optical-grade silicone, deposited on the LED devices.
The LED must maintain its junction temperature in the proper rated range to maximize efficacy, longevity, and reliability. The enclosure of the light engine must provide for dissipation of the heat generated by the LEDs. Many LED lights are housed within finned fixtures. The fins dissipate the heat to ambient surroundings. LED lighting finds many uses for indoor applications or settings that are not subject to weather elements. However, the air-cooled finned fixtures are not suitable for outdoor applications, which are subject to moisture or that must otherwise be sealed against the elements.
While water-tight or sealed light fixtures are known, such enclosures are designed for conventional light sources, i.e., incandescent or halogen bulbs, and do not address the heat dissipation requirement of LED lights. In fact, the sealed fixture behaves as a thermal insulator and encloses the heat within the fixture. In conventional light bulbs there is no effective mechanism or even need to transfer heat from the light element or gases sealed within the bulb to ambient surroundings. Conventional light bulbs and fixtures carry a rating for a maximum wattage bulb that can be used in the fixture and therefore do not require a heat sink. Accordingly, conventional sealed fixtures have no effective heat transfer capability and therefore are not suitable for LED light engines, as the heat would be trapped within the fixture and reduce the life expectancy and reliability of the LEDs.
A need exists for an LED light engine compatible with a sealed or submersible fixture.